U.S. patent application number 13/211390 was filed with the patent office on 2012-02-23 for blood pressure measuring apparatus.
This patent application is currently assigned to NIHON KOHDEN CORPORATION. Invention is credited to Hideaki HIRAHARA, Yoshiharu KIKUCHI, Naoki KOBAYASHI, Katsuyoshi SUZUKI, Takashi USUDA.
Application Number | 20120046561 13/211390 |
Document ID | / |
Family ID | 44719262 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120046561 |
Kind Code |
A1 |
USUDA; Takashi ; et
al. |
February 23, 2012 |
BLOOD PRESSURE MEASURING APPARATUS
Abstract
A blood pressure measuring apparatus, which measures a blood
pressure of a living body, includes: a cuff-pressure control unit
which controls a cuff pressure of a cuff that presses a part of the
living body; an oscillation signal detection unit which detects an
oscillation signal from the cuff pressure; a blood pressure
specification unit which specifies systolic and diastolic blood
pressures as the blood pressure of the living body from the
oscillation signal; and a blood pressure determination unit which
determines whether systolic and diastolic blood pressures are
appropriate or not. The cuff-pressure control unit controls the
cuff pressure to be inflated to a first set value, the blood
pressure specification unit specifies the systolic and diastolic
blood pressures based on a change of an oscillation signal that is
detected by the oscillation signal detection unit when the cuff
pressure is inflated to the first set value, and when the blood
pressure determination unit determines that both the systolic and
diastolic blood pressures are appropriate, the cuff-pressure
control unit ends the inflating of the cuff pressure to release the
cuff pressure.
Inventors: |
USUDA; Takashi; (Tokyo,
JP) ; KIKUCHI; Yoshiharu; (Tokyo, JP) ;
HIRAHARA; Hideaki; (Tokyo, JP) ; KOBAYASHI;
Naoki; (Tokyo, JP) ; SUZUKI; Katsuyoshi;
(Tokyo, JP) |
Assignee: |
NIHON KOHDEN CORPORATION
Tokyo
JP
|
Family ID: |
44719262 |
Appl. No.: |
13/211390 |
Filed: |
August 17, 2011 |
Current U.S.
Class: |
600/494 |
Current CPC
Class: |
A61B 5/02141 20130101;
A61B 5/0225 20130101; A61B 5/02225 20130101; A61B 5/02116
20130101 |
Class at
Publication: |
600/494 |
International
Class: |
A61B 5/0225 20060101
A61B005/0225 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2010 |
JP |
2010-182150 |
Claims
1. A blood pressure measuring apparatus, which measures a blood
pressure of a living body, the blood pressure measuring apparatus
comprising: a cuff-pressure control unit which controls a cuff
pressure of a cuff that presses a part of the living body; an
oscillation signal detection unit which detects an oscillation
signal from the cuff pressure; a blood pressure specification unit
which specifies systolic and diastolic blood pressures as the blood
pressure of the living body from the oscillation signal; and a
blood pressure determination unit which determines whether systolic
and diastolic blood pressures are appropriate or not, wherein the
cuff-pressure control unit controls the cuff pressure to be
inflated to a first set value, the blood pressure specification
unit specifies the systolic and diastolic blood pressures based on
a change of an oscillation signal that is detected by the
oscillation signal detection unit when the cuff pressure is
inflated to the first set value, and when the blood pressure
determination unit determines that both the systolic and diastolic
blood pressures are appropriate, the cuff-pressure control unit
ends the inflating of the cuff pressure to release the cuff
pressure.
2. The blood pressure measuring apparatus according to claim 1,
further comprising: an air pump which is controlled by the
cuff-pressure control unit to eject air to the cuff, thereby
inflating the cuff pressure, wherein the cuff-pressure control unit
controls the air pump to eject air to the cuff with a cycle which
is different from a cycle of a pulse wave.
3. The blood pressure measuring apparatus according to claim 2,
wherein the cuff-pressure control unit controls the air pump so
that the cycle at which the air pump ejects air is a cycle is which
is shorter than at least one fifth of the cycle of the pulse
wave.
4. The blood pressure measuring apparatus according to claim 2,
wherein a flow of air ejected by the air pump is from 0.1 L/minute
to 3.0 L/minute.
5. The blood pressure measuring apparatus according to claim 1,
wherein the cuff-pressure control unit controls the cuff pressure
to be inflated in a substantially linear manner.
6. The blood pressure measuring apparatus according to claim 1,
wherein when the blood pressure determination unit determines that
at least one of the systolic and diastolic blood pressures is not
appropriate, the cuff-pressure control unit controls the cuff
pressure to be inflated to a second set value, and then deflated,
and the blood pressure specification unit specifies the systolic
and diastolic blood pressures based on a change of an oscillation
signal that is detected by the oscillation signal detection unit
when the cuff pressure is deflated from the second set value.
7. The blood pressure measuring apparatus according to claim 6,
wherein the cuff-pressure control unit controls the cuff pressure
to be deflated in a stepwise manner.
8. The blood pressure measuring apparatus according to claim 6,
wherein the cuff-pressure control unit controls the cuff pressure
to be deflated in a substantially linear manner.
9. The blood pressure measuring apparatus according to claim 6,
wherein the first set value is a value which is lower than the
second set value, the first set value is a value which is higher
than a systolic blood pressure of the living body, and the second
set value is a value which is higher than a value in which at least
30 mmHg to 50 mmHg is added to a systolic blood pressure of the
living body.
10. The blood pressure measuring apparatus according to claim 1,
further comprising: a cuff-size specification unit which specifies
a size of the cuff when the cuff pressure is to be inflated,
wherein the cuff-pressure control unit controls pressure inflating
of the cuff based on the size of the cuff which is specified by the
cuff-size specification unit.
11. The blood pressure measuring apparatus according to claim 1,
wherein the cuff-pressure control unit inflates or deflates the
cuff pressure in a range of 5 mmHg/sec. to 20 mmHg/sec.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a blood pressure measuring
apparatus which non-invasively measures the blood pressure.
[0002] As a blood pressure measuring apparatus which non-invasively
measures the blood pressure, a blood pressure measuring apparatus
is usually employed in which the blood pressure is measured by
first inflating the cuff pressure to a pressure that is
sufficiently higher than the systolic blood pressure (for example,
a cuff pressure that is higher than the systolic blood pressure by
40 mmHg), and, while then deflating the cuff pressure, detecting
pressure oscillation that is produced in the cuff pressure by
pulsation, as an oscillation signal. There is a blood pressure
measuring apparatus in which the blood pressure is measured while
inflating the cuff pressure, in order to shorten the time required
for measurement as compared with the blood pressure measurement
that measures the blood pressure while deflating the cuff pressure
(for example, see JP-A-8-322811).
[0003] In the process of inflating the cuff pressure, however, air
is ejected from an air pump to a cuff, and hence periodic
oscillation due to driving of the air pump is superimposed as noise
on pressure oscillation in the cuff caused by pulsation. In the
case where the cycle of the oscillation due to driving of the air
pump is similar to that of the pulsation component which is a
principal component of a pulse wave, therefore, it is difficult to
measure a correct blood pressure from the oscillation signal.
[0004] In the related-art blood pressure measurement performed
during the process of deflating the cuff pressure, when the
systolic blood pressure is to be measured, moreover, the cuff must
be pressurized by a pressure which is sufficiently higher than the
systolic blood pressure. The pressurization may sometimes cause a
burden on the subject (the patient or the like). Therefore, it is
requested to develop accurate blood pressure measurement in which
the burden on the patient is low, and which can be rapidly
performed.
SUMMARY
[0005] It is therefore an object of the invention to provide a
blood pressure measuring apparatus which can solve the problem that
oscillation due to driving of the air pump is superimposed as noise
on an oscillation signal and an accurate blood pressure cannot be
obtained.
[0006] In order to achieve the object, according to the invention,
there is provided a blood pressure measuring apparatus, which
measures a blood pressure of a living body, the blood pressure
measuring apparatus comprising: a cuff-pressure control unit which
controls a cuff pressure of a cuff that presses a part of the
living body; an oscillation signal detection unit which detects an
oscillation signal from the cuff pressure; a blood pressure
specification unit specifies systolic and diastolic blood pressures
as the blood pressure of the living body from the oscillation
signal; and a blood pressure determination unit which determines
whether systolic and diastolic blood pressures are appropriate or
not, wherein the cuff-pressure control unit controls the cuff
pressure to be inflated to a first set value, the blood pressure
specification unit which specifies the systolic and diastolic blood
pressures based on a change of an oscillation signal that is
detected by the oscillation signal detection unit when the cuff
pressure is inflated to the first set value, and when the blood
pressure determination unit determines that both the systolic and
diastolic blood pressures are appropriate, the cuff-pressure
control unit ends the inflating of the cuff pressure to release the
cuff pressure.
[0007] The blood pressure measuring apparatus may further include
an air pump which is controlled by the cuff-pressure control unit
to eject air to the cuff, thereby inflating the cuff pressure. The
cuff-pressure control unit may control the air pump to eject air to
the cuff with a cycle which is different from a cycle of a pulse
wave.
[0008] The cuff-pressure control unit may control the air pump so
that the cycle at which the air pump ejects air is a cycle which is
shorter than at least one fifth of the cycle of the pulse wave.
[0009] A flow of air ejected by the air pump may be from 0.1
L/minute to 3.0 L/minute.
[0010] The cuff-pressure control unit may control the cuff pressure
to be inflated in a substantially linear manner.
[0011] When the blood pressure determination unit determines that
at least one of the systolic and diastolic blood pressures is not
appropriate, the cuff-pressure control unit may control the cuff
pressure to be inflated to a second set value, and then deflated,
and the blood pressure specification unit may specify the systolic
and diastolic blood pressures based on a change of an oscillation
signal that is detected by the oscillation signal detection unit
when the cuff pressure is deflated from the second set value.
[0012] The cuff-pressure control unit may control the cuff pressure
to be deflated in a stepwise manner.
[0013] The cuff-pressure control unit may control the cuff pressure
to be deflated in a substantially linear manner.
[0014] The first set value may be a value which is lower than the
second set value, the first set value may be a value which is
higher than a systolic blood pressure of the living body, and the
second set value may be a value which is higher than a value in
which at least 30 mmHg to 50 mmHg is added to a systolic blood
pressure of the living body.
[0015] The blood pressure measuring apparatus may further include a
cuff-size specification unit which specifies a size of the cuff
when the cuff pressure is to be inflated. The cuff-pressure control
unit may control pressure inflating of the cuff based on the size
of the cuff which is specified by the cuff-size specification
unit.
[0016] The cuff-pressure control unit may inflate or deflate the
cuff pressure in a range of 5 mmHg/sec. to 20 mmHg/sec.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a functional block diagram schematically showing a
blood pressure measuring apparatus of an embodiment of the
invention.
[0018] FIG. 2 is a flowchart (No. 1) illustrating the operation of
the blood pressure measuring apparatus.
[0019] FIG. 3 is a flowchart (No. 2) illustrating the operation of
the blood pressure measuring apparatus.
[0020] FIG. 4 is a view showing an oscillation signal and the
waveform of a cuff pressure in blood pressure measurement during a
process of inflating the cuff pressure in the blood pressure
measuring apparatus.
[0021] FIG. 5 is a view showing the oscillation signal and the
waveform of the cuff pressure in blood pressure measurement during
a process of deflating the cuff pressure in the blood pressure
measuring apparatus.
DETAILED DESCRIPTION OF EMBODIMENTS
[0022] Hereinafter, a blood pressure measuring apparatus 100 of an
embodiment of the invention will be described in detail with
reference of the drawings. FIG. 1 is a functional block diagram
schematically showing the blood pressure measuring apparatus 100.
As shown in FIG. 1, the blood pressure measuring apparatus 100
includes a cuff 1, a pressure sensor 2, an air pump 3, an
electromagnetic valve 4, a DC amplifier 6, A/D converters 7, 9, an
AC amplifier 8, a BPF (Band Pass Filter) 10, a pump controller 11,
an electromagnetic-valve driver 12, a controller 13, a key panel
14, and a liquid crystal display (LCD) 15.
[0023] In the blood pressure measuring apparatus 100, the pump
controller 11, the air pump 3, the electromagnetic-valve driver 12,
the electromagnetic valve 4, and the controller 13 function as the
cuff-pressure control unit in the invention to control a cuff
pressure of a cuff that presses a part of a living body.
[0024] The pressure sensor 2, the DC amplifier 6, the A/D
converters 7, 9, the AC amplifier 8, the BPF (Band Pass Filter) 10,
and the controller 13 function as the oscillation signal detection
unit in the invention to detect an oscillation signal from the cuff
pressure.
[0025] The controller 13 functions also as the blood pressure
specification unit and the blood pressure determination unit in the
invention, specifies the systolic and diastolic blood pressures as
the blood pressure of the living body based on a change of the
detected oscillation signal, and determines whether the blood
pressure is appropriate or not. The controller 13 functions also as
the cuff-size specification unit in the invention, and specifies
the size of the cuff when the cuff pressure is to be inflated.
[0026] The cuff 1 is wrapped around the finger, the upper arm, a
lower leg, or the like of the subject. Air ejected from the air
pump 3 in which the principal frequency (usually, 5 Hz or lower) of
the oscillation signal is different from that (at least 30 Hz or
higher) of ejection noise of air is fed to the cuff 1, and the cuff
pressure is inflated. The pump controller 11 controls a driving
power to be supplied to the air pump 3, and the cycle of air
ejection in accordance with a control signal C1 which is supplied
from a CPU (Central Processing Unit) 13b through an I/O port
(Input/Output port) 13a.
[0027] The air pump 3 is a low-flow air pump such as a rolling pump
having a plurality of cylinders (for example, two, three, or four
cylinders), and, when the cuff 1 is to be pressurized, is high
speed driven. More specifically, the air pump 3 is driven so that
the cycle of oscillation due to the operation of ejecting air is
very shorter (for example, one fifth or smaller) than that of the
principal component of a pulse wave (time waveform of pulsation).
In the case where, as described above, the air pump of a low flow
(about 0.1 L/minute) is driven (high-speed driven) with a cycle
which is very shorter than that of a pulse wave, when a pulse wave
is to be measured, the oscillation component of the pressure of air
ejected from the air pump 3 can be easily cancelled as described
later.
[0028] As the air pump 3, an air pump in which the flow of ejected
air can be continuously changed from a low flow (about 0.1
L/minute) to a high flow (about 3 L/minute) by changing the driving
power and the cycle of air ejection may be used.
[0029] The electromagnetic-valve driver 12 receives a control
signal C2 from the CPU 13b through the I/O port 13a, and drives the
electromagnetic valve 4 in accordance with the contents of the
control signal C2, to exhaust the air in the cuff 1.
[0030] The pressure sensor 2 detects the air pressure in the cuff
1, i.e., the cuff pressure. An output signal from the pressure
sensor 2 undergoes in the DC amplifier 6, a process in which a DC
component (a component which does not depend on periodic variations
due to a pulse wave or the like) of the signal is amplified, and
then is converted to a digital signal in the A/D converter
(analog/digital converting circuit) 7. The digital signal which is
converted in the A/D converter 7 is sent to the CPU 13b through the
I/O port 13a, as a pressure signal D in which the DC component is
emphasized.
[0031] Also, the output signal of the DC amplifier 6 is subjected
to a process in which an AC component (periodic variation component
in which a pulse wave component is the principal component) is
amplified, and the components other than the pulse wave component
is filtered by the BPF 10. As described above, the driving cycle of
the air pump 3 is very shorter than the cycle of the principal
component of the pulse wave. Therefore, the pulse wave component
can be easily separated from the oscillation components of the
pressure of the air ejected from the air pump 3.
[0032] The A/D converter 9 converts the signal which is filtered by
the BPF 10, to a digital signal. The digital signal which is
converted in the A/D converter 9 is sent to the CPU 13b through the
I/O port 13a, as a pressure signal M containing the principal
component of the pulse wave.
[0033] The key panel 14 is a controller in which operation keys for
performing various operations such as instructions for starting
measurement are arranged, and connected to the I/O port 13a. Also
the liquid crystal display (LCD) 15 which displays the blood
pressure and the like of measurement results on a screen is
connected to the I/O port 13a. Displaying means which can display
the blood pressure and the like of measurement results on a screen
may be, for example, an LED or an organic EL display in place of
the liquid crystal display (LCD) 15 in the embodiment.
[0034] The controller 13 includes the CPU 13b, the I/O port 13a, a
PAM 13c, and a ROM 13d, and controls various parts of the blood
pressure measuring apparatus 100. The controller 13 processes
various input and detection signals supplied from the parts, and
outputs various control signals and a measurement result based on
the results of the processes.
[0035] The I/O port 13a is an input/output port for the CPU 13b,
and connected to the A/D converters 7, 9, the pump controller 11,
and the electromagnetic-valve driver 12. The pressure signals D and
M which are converted by the A/D converters 7, 9 are supplied to
the CPU 13b trough the I/O port 13a, and control signals from the
CPU 13b are sent to the pump controller 11 and the
electromagnetic-valve driver 12 through the I/O port 13a.
[0036] The RAM (Random Access Memory) 13c which is data holding
means connected to the CPU 13b sequentially stores data of
processing processes. The ROM (Read-Only memory) 13d which is
connected to the CPU 13b stores process programs of the CPU
13b.
[0037] The CPU 13b calculates the value of the oscillation signal
based on the input pressure signals D and M. Then, the CPU 13b
performs sampling at each predetermined timing of the calculated
waveform of the oscillation signal, and calculates the amplitude.
When the cuff pressure is inflated, the calculated amplitude is
gradually increased. After the timing when the amplitude becomes
maximum, the calculated amplitude is gradually decreased.
[0038] Based on a change of the oscillation amplitude due to a
temporal change of the cuff pressure, the CPU 13b specifies the
systolic and diastolic blood pressures as blood pressures of the
subject. Then, the CPU 13b determines whether the blood pressures
are appropriate or not. More specifically, the CPU 13b determines
whether the specified blood pressures are an inappropriate blood
pressure due to body motion or arrhythmia of the subject or not,
based on previously stored criteria. If both the specified systolic
and diastolic blood pressures are determined as a appropriate
value, the CPU 13b sends the control signal C1 indicating that the
driving of the air pump 3 is stopped, to the pump controller 11 in
order that the cuff pressure is inflated to a first set value and
then the pressure rising is ended. Furthermore, the CPU 13b sends
the control signal C2 indicating that the electromagnetic valve 4
is fully opened and air in the cuff 1 is exhausted, to the
electromagnetic-valve driver 12 in order that, when the rising of
the cuff pressure is ended, the cuff pressure is immediately
released. The first set value is higher than the systolic blood
pressure, and lower than a set value (preferably, a value which is
higher than the systolic blood pressure by about 30 to 50 mmHg,
hereinafter referred to as the second set value) which is used in
usual pressure-deflating measurement.
[0039] The first set value may be a fixed value, or a value which
can be adequately changed based on a change of the oscillation
amplitude that is obtained during pressure-inflating
measurement.
[0040] By contrast, if at least one of the systolic and diastolic
blood pressures is not determined as a appropriate value, the CPU
13b sends the control signal C1 indicative of the driving of the
air pump 3 until the cuff pressure reaches a preset pressurization
target (second set value), to the pump controller 11. When the cuff
pressure reaches the pressurization target, the CPU 13b sends the
control signal C2 indicating that the electromagnetic valve 4 is
intermittently opened and the cuff pressure is deflated in a
stepwise manner, to the electromagnetic-valve driver 12. Then, the
CPU 13b calculates the value of the oscillation signal when the
cuff pressure is deflated, in the same manner as described above,
and, based on a change of the value, specifies the systolic and
diastolic blood pressures of the subject. Although the blood
pressure measurement performed while deflating the cuff pressure in
a stepwise manner requires a prolonged time cycle as compared with
that performed while deflating the cuff pressure in a linear
manner, the blood pressure measurement can surely measure the
oscillation signal, and hence can be accurately performed.
[0041] Next, the operation of the blood pressure measuring
apparatus of the embodiment of the invention will be described with
reference to FIGS. 2 and 3. FIG. 2 is a flowchart (No. 1)
illustrating the operation of the blood pressure measuring
apparatus 100, and FIG. 3 is a flowchart (No. 2) illustrating the
operation of the blood pressure measuring apparatus 100.
[0042] First, the cuff 1 is wrapped around a finger or upper arm
portion of the subject, and then a button for starting the
measurement in the key panel 14 is pressed. The CPU 13b sends the
control signal C1 to the pump controller 11 while setting the
driving power of the air pump 3 to a predetermined value (for
example, the duty of driving power of the air pump is set to 100%).
The pump controller 11 drives the air pump 3 with constant driving
power to inflate the cuff pressure (step S1). The duty of driving
power of the air pump is a ratio of the pulse interval and the
pulse width in the case where the air pump 3 is driven by giving a
voltage pulse of a constant interval to the air pump.
[0043] In next step S2, the CPU 13b determines whether the cuff
pressure due to the pressure signal D is higher than a first cuff
pressure P1 (for example, 15 mmHg) that is lower than the minimum
pressure or not. The air pump 3 is controlled through the pump
controller 11 so as to inflate the cuff pressure until the
determination in step S2 is YES.
[0044] If the determination in step S2 is YES, the CPU 13b starts
the time count, and determines whether the cuff pressure is higher
than a second cuff pressure P2 (for example, 20 mmHg) that is lower
than the minimum pressure or not (step S3).
[0045] The first cuff pressure P1 is requested to be a value in the
range between 15 mmHg and 45 mmHg, the second cuff pressure P2 is
requested to be a value in the range between 20 mmHg and 50 mmHg,
and the pressures are requested to satisfy the relationship of
P1<P2.
[0046] If the determination in step S3 is YES, the CPU 13b
terminates the time counting, calculates the cuff capacity value
from the counted time cycle (the time required for inflating from
P1 to P2) and the air election amount of the air pump 3 per unit
time, and stores the obtained cuff capacity value in the RAM 13c
(step S4: cuff capacity measurement).
[0047] Namely, when the cuff capacity value is measured in the
above-described procedure, the controller 13 functions as a
cuff-size specification unit which specifies the size of the cuff
when the cuff pressure is inflated.
[0048] Next, the CPU 13b calculates the duty of driving power of
the air pump and the pump ejection cycle (the cycle at which air is
ejected) in the subsequent inflating of the pressure in accordance
with the cuff capacity value (stored in the RAM 13c) which is
obtained in the cuff capacity measurement in step S4, and changes
the control signal C1 so as to drive the air pump 3 at the duty of
driving power of the air pump and pump ejection cycle which are
calculated (step S5).
[0049] In accordance with the change, the pump controller 11 drives
the air pump 3 in accordance with the duty of driving power of the
air pump and pump election cycle which are changed, to inflate the
cuff pressure to the first set value (step S6).
[0050] Namely, the cuff-pressure control unit controls the
inflating of the pressure of the cuff based on the cuff capacity
value (the specified cuff size) which is measured in the above
procedure.
[0051] As described above, based on the cuff capacity value, i.e.,
the size of the capacity of the cuff 1, the driving ability (more
specifically, the inclination of the line in the case where the
cuff pressure is inflated in a linear manner) of the air pump 3
when the cuff pressure is inflated can be changed, and hence it is
possible to cope with cuffs of different sizes.
[0052] In step S6 above, the cuff pressure is inflated by driving
the air pump 3, and the cuff pressure D.sub.1 due to the pressure
signal D which is detected by the pressure sensor 2 is inflated as
shown in FIG. 4. FIG. 4 is a view showing the oscillation signal
and the waveform of the cuff pressure in blood pressure measurement
during a process of inflating the cuff pressure in the blood
pressure measuring apparatus 100. At this time, as the pressure
inflating rate, a constant rate in the range of, for example, 5
mmHg/sec. to 20 mmHg/sec. is set as a target. As shown in FIG. 4,
when the cuff pressure is inflated, the detected oscillation signal
becomes the diastolic blood pressure (minimum blood pressure) at a
change point T.sub.L where the amplitude is suddenly increased, the
amplitude is gradually reduced after the amplitude is increased and
becomes maximum, and the detected oscillation signal becomes the
systolic blood pressure (maximum blood pressure) at a change point
T.sub.H where the amplitude is suddenly reduced.
[0053] When the cuff pressure is inflated, the CPU 13b performs
sampling to obtain the amplitude, as described above, finds a
change point where the amplitude is suddenly changed, and specifies
the diastolic blood pressure (minimum blood pressure) and the
systolic blood pressure (maximum blood pressure) (step S7). Then,
the CPU 13b determines whether both the diastolic blood pressure
(minimum blood pressure) and the systolic blood pressure (maximum
blood pressure) can be specified or not (step S8). The systolic
blood pressure (maximum blood pressure) may be set to be a value at
a timing when the amplitude is smaller than the maximum amplitude
of the oscillation signal by a predetermined ratio (for example, an
amplitude which is a half of the maximum amplitude).
[0054] In the process of specifying the systolic and diastolic
blood pressures, any related-art technique may be employed in place
of the above-described technique. For example, a cuff pressure at a
timing when the amplitude is at 50% of the maximum amplitude of the
oscillation signal may be specified as the systolic and diastolic
blood pressures.
[0055] If the determination in step S8 is YES, the CPU 13b
transmits the control signal C2 to the electromagnetic-valve driver
12 to fully open the electromagnetic valve 4, thereby rapidly
deflating the cuff pressure D.sub.1 which has reached the first set
value (step S9). Then, the CPU 13b stores the specified blood
pressures in the RAM 13c or displays the blood pressures on the LCD
15, or performs the both operations (step S10), and ends the blood
pressure measurement.
[0056] By contrast, if the determination in step S8 is NO, the CPU
13b determines whether the cuff pressure is equal to or higher than
the second set value or not (step S11). The operation of inflating
the cuff pressure is continued until the determination in step S8
becomes YES or that in step S11 becomes YES (the cuff pressure
reaches the second set value). If the determination in step S11
becomes YES, the pressure-deflating measurement such as shown in
FIG. 5 is performed. FIG. 5 is a view showing the oscillation
signal and the waveform of the cuff pressure in blood pressure
measurement during the process of deflating the cuff pressure in
the blood pressure measuring apparatus 100. In the
pressure-deflating measurement, the CPU 13b transmits the control
signal C2 to the electromagnetic-valve driver 12, and controls the
opening of the electromagnetic valve 4 to lower the cuff pressure
in a stepwise manner (step S12). As a result, as shown in FIG. 5,
the cuff pressure D.sub.2 due to the pressure signal D is deflated
in a stepwise manner.
[0057] As shown in FIG. 5, as the cuff pressure D.sub.2 is further
deflated, the detected oscillation signal becomes the systolic
blood pressure (maximum blood pressure) at a change point T.sub.H
where the amplitude is suddenly increased, the amplitude is
gradually reduced after the amplitude is increased and becomes
maximum, and the detected oscillation signal becomes the diastolic
blood pressure (minimum blood pressure) at a change point T.sub.L
where the amplitude is suddenly reduced.
[0058] During the process of deflating the cuff pressure, the CPU
13b performs sampling on the oscillation signal to obtain the
amplitude, as described above, finds a change point where the
amplitude is suddenly changed, and specifies the diastolic blood
pressure (minimum blood pressure) and the systolic blood pressure
(maximum blood pressure) (step S13). Then, the CPU 13b determines
whether both the diastolic blood pressure (minimum blood pressure)
and the systolic blood pressure (maximum blood pressure) can be
specified or not (step S14).
[0059] Similarly as described above, in the process of specifying
the systolic and diastolic blood pressures, any related-art
technique may be employed in place of the above-described
technique. For example, a cuff pressure at a timing when the
amplitude is at 50% of the maximum amplitude of the oscillation
signal may be specified as the systolic and diastolic blood
pressures.
[0060] If the determination in step S14 is YES, the CPU 13b
transmits the control signal C2 to the electromagnetic-valve driver
12 to fully open the electromagnetic valve 4, thereby rapidly
deflating the cuff pressure D.sub.2 (step S15). Then, the CPU 13b
stores the measured blood pressures in the RAM 13c or displays the
blood pressures on the LCD 15, or performs the both operations
(step S16), and ends the blood pressure measurement.
[0061] In the embodiment, the blood pressure measurement during the
process of deflating the cuff pressure is performed while deflating
the cuff pressure in a stepwise manner. Similarly as the blood
pressure measurement during the process of inflating the cuff
pressure, alternatively, the blood pressure measurement may be
performed while deflating the cuff pressure in a linear manner. In
the alternative, as compared with the case where the blood pressure
measurement is performed while deflating the cuff pressure in a
stepwise manner, when the subject experiences arrhythmia or body
motion is caused, rapid blood pressure measurement is often enabled
although the accuracy is impaired.
[0062] By contrast, if the determination in step S14 is NO, the CPU
13b determines whether the cuff pressure D.sub.2 is equal to or
lower than a predetermined value or not (step S17). The operation
of deflating the cuff pressure in a stepwise manner is continued
until the determination in step S14 becomes YES or that in step S17
becomes YES.
[0063] If the determination in step S17 is YES, the CPU 13b
transmits the control signal C2 to the electromagnetic-valve driver
12 to fully open the electromagnetic valve 4, thereby rapidly
deflating the cuff pressure D.sub.2 (step S18). Then, contents
indicating that blood pressure measurement was disabled are
displaced on the LCD 5 (step S19).
[0064] As described above, according to the blood pressure
measuring apparatus of the embodiment, even in the case where,
during the process of inflating the cuff pressure, oscillation due
to driving of the air pump is superimposed as noise on pressure
oscillation in the cuff caused by pulsation, the cycle of
oscillation due to the driving of the air pump is largely different
from that (pulsation cycle) of the principal component of a pulse
wave. Therefore, it is possible to measure a correct blood pressure
from the oscillation signal which is detected when the cuff
pressure is inflated. In the case where the measured blood pressure
is appropriate, the inflating of the cuff pressure is ended and the
cuff pressure is immediately released. Therefore, the measurement
time can be shortened, and hence the burden on the subject (the
patient or the like) due to the measurement is low.
[0065] Even in the case where during the process of inflating the
cuff pressure a appropriate blood pressure cannot be measured
because body motion, arrhythmia, or the like of the subject, the
blood pressure can be then measured by pressure-deflating
measurement in which the cuff pressure that is hardly affected by
body motion, arrhythmia, or the like is deflated in a stepwise
manner.
[0066] In the blood pressure measuring apparatus of the invention,
when both the systolic and diastolic blood pressures which are
measured in the process of inflating the cuff pressure are
appropriate, the pressure is rapidly deflated. Therefore, it is
possible to realize accurate blood pressure measurement which can
be rapidly performed, and in which the burden on the subject (the
patient or the like) is low.
[0067] Moreover, the cycle of air ejection by the air pump is
different from that of the pulse wave, and hence ejection noise due
to the operation of the air pump is superimposed as obvious noise
on the oscillation signal. Therefore, the ejection noise can be
distinctly removed, and hence it is possible to perform accurate
blood pressure measurement.
[0068] The air pump ejects air with a short cycle (a cycle which is
shorter than at least one fifth of a cycle of the principal
component of the pulse wave). Therefore, the cuff can be
pressurized in a substantially linear manner, and rapid blood
pressure measurement is realized in the process of inflating the
cuff pressure.
[0069] The flow of air ejected by the air pump can be continuously
changed from a low flow (about 0.1 L/minute) to a high flow (about
3 L/minute). Therefore, the pressurization is not performed in a
stepwise manner, and rapid blood pressure measurement is realized
in the process of inflating the cuff pressure.
[0070] Since the pressure is inflated in a substantially linear
manner, rapid blood pressure measurement is realized in the process
of inflating the cuff pressure.
[0071] In the case where the blood pressure measurement in pressure
inflating is inappropriate (the measurement value is not a
appropriate value), the cuff is further pressurized to the second
set value, and the usual blood pressure measurement performed
during the process of deflating the cuff pressure can be performed.
Therefore, rapid blood pressure measurement is realized.
Particularly, rapid blood pressure measurement is realized in the
process of inflating the cuff pressure, and accurate blood pressure
measurement is realized in the process of deflating the cuff
pressure, so that blood pressure measurement can be surely
performed by one process of inflating and deflating the cuff
pressure. Therefore, the number of occurrences of remeasuring the
blood pressure can be reduced.
[0072] The pressure is deflated in a stepwise manner. Even in the
case where the subject (the patient or the like) experiences
arrhythmia or body motion is caused, therefore, the oscillation
signal can be surely detected, with the result that rapid and
accurate blood pressure measurement is realized. Alternatively, the
pressure is deflated in a substantially linear manner, and hence
rapid blood pressure measurement is realized in the process of
deflating the cuff pressure.
[0073] The first set value in the process of inflating the cuff
pressure is lower than the related-art set value (second set
value). When blood pressure measurement in the process of inflating
the cuff pressure is appropriate, therefore, blood pressure
measurement which is rapid, and in which the burden is low is
realized.
[0074] The pressure can be inflated in accordance with the size of
the cuff, and the blood pressure measurement can be accurately
performed in the process of inflating the cuff pressure.
* * * * *